you haven't said for which exam they're offering this. For the Red Badge, I wouldn't go near the place.
For Foundations, it can be a solution, but my opinion is that reading the book is essential, and you might be better off with an online course for Foundations and reading.
And there is also the Practicioner exam, which is more focussed.
All in all, it might be a complementary element, but I don't think it's enough to do the bootcamp only.